Since the invention of the integrated circuit (IC), the semiconductor industry has experienced continued rapid growth due to continuous improvements in the integration density of various electronic components (e.g., transistors, diodes, resistors, capacitors, etc.). For the most part, this improvement in integration density has come from repeated reductions in minimum feature size, which allows more components to be integrated into a given area.
The past few decades have also seen many shifts in semiconductor packaging that have impacted the entire semiconductor industry. The introduction of surface-mount technology (SMT) and ball grid array (BGA) packages were generally important steps for high-throughput assembly of a wide variety of IC devices, while at the same time allowing for reduction of the pad pitch on the printed circuit board. Conventionally packaged ICs have a structure basically interconnected by fine gold wire between metal pads on the die and electrodes spreading out of molded resin packages. On the other hand, some CSP or BGA packages rely on bumps of solder to provide an electrical connection between contacts on the die and contacts on a substrate, such as a packaging substrate, a printed circuit board (PCB), another die/wafer, or the like. Other CSP or BGA packages utilize a solder ball or bump placed onto a conductive pillar, relying on the soldered joint for structural integrity. In these situations, it is typical to cover the substrate around the solder balls or bumps with a polymer material to protect the surface of the substrate. An underfill material is also typically placed between the IC and the underlying substrate, e.g., packaging substrate, to provide mechanical strength and to protect the IC from environmental contaminants.
In some devices, the polymer surface was purposefully roughened, thereby creating a coral-like surface. This roughened surface was believed to create a stronger bond between the polymer material and the underfill material, reducing delamination between the underfill material and the polymer surface. It has been found, however, that this roughened surface also induces additional contaminants during processing. For example, the roughened surface appears to increase the amount of tape residue from applying tape during a backside thinning process.